On Tue, 11 Apr 2017 14:56:56 -0700 "Paul E. McKenney" <[email protected]> wrote:
> On Tue, Apr 11, 2017 at 05:49:53PM -0400, Steven Rostedt wrote: > > On Tue, 11 Apr 2017 14:44:43 -0700 > > "Paul E. McKenney" <[email protected]> wrote: > > > > > > > Works for me! > > > > > > Hopefully it will also work for your computer. :-) > > > > > > And whew! Glad to see that the stall warnings worked! > > > > Ah! but I think I found a bug in synchronize_rcu_tasks()! > > > > Calling schedule isn't good enough. For rcu_tasks to continue, the task > > needs to schedule out. With my updated code, I just triggered: > > > > [ 196.276868] INFO: rcu_tasks detected stalls on tasks: > > [ 196.284294] ffff8800c26f8040: .. nvcsw: 2/2 holdout: 1 idle_cpu: -1/1 > > [ 196.293175] event_benchmark R running task 30536 1127 2 > > 0x10000000 > > [ 196.302746] Call Trace: > > [ 196.307640] ? _raw_spin_unlock_irq+0x1f/0x50 > > [ 196.314453] __schedule+0x222/0x1210 > > [ 196.320476] ? pci_mmcfg_check_reserved+0xc0/0xc0 > > [ 196.327616] ? preempt_count_add+0xb7/0xf0 > > [ 196.334174] ? __asan_store8+0x15/0x70 > > [ 196.340384] schedule+0x57/0xe0 > > [ 196.345888] benchmark_event_kthread+0x2e/0x3c0 > > [ 196.352823] kthread+0x178/0x1d0 > > [ 196.358411] ? trace_benchmark_reg+0x80/0x80 > > [ 196.365073] ? kthread_create_on_node+0xa0/0xa0 > > [ 196.371999] ret_from_fork+0x2e/0x40 > > > > > > And here my benchmark called schedule(), but nothing scheduled it out, > > and it still fails on rcu_tasks. > > Good point! > > Hmmmm... I cannot hook into rcu_note_context_switch() because that gets > called for preemption as well as for voluntary context switches. If you pass in the "preempt" variable, it would work. It's false when __schedule() was called by a "schedule()" directly, and true when called by one of the preempt_schedule() functions. -- Steve > > How about cond_resched_rcu_qs()? Does that cover it? > > Thanx, Paul
